Stomatogenic events accompanying binary fission in Blepharisma

Oral assembly in left-handed Tetrahymena thermophila

We have investigated oral development in a non-genetically derived left-handed (LH) form of Tetrahymena thermophila, in which the large-scale asymmetry of arrangement of cortical structures is reversed whereas the local asymmetry of ciliary architecture remains normal. Approximately 1/2 of the oral apparatuses (OAs) of LH cells develop in the form of superficial mirror-images of OAs of RH cells. In most of these OAs, membranelles are assembled from the cells' anterior to posterior. Nonetheless, the posterior ends of these membranelles undergo the basal body displacements that lead to a "sculptured" appearance, so that the membranelles of LH OAs become organized as rotational permutations of membranelles of normal RH OAs. Many of these membranelles re-orient to a normal orientation near the end of oral development. Membranelles and undulating membranes (UMs) may develop independently of each other, and formation of postciliary microtubules of UMs is separate from that of ribbed wall microtubules. In some cases, the entire OA develops and remains as a 180 degrees rotational permutation of the normal, resembling the inverted OAs of mirror-image doublets and LH cells of Glaucoma scintillans described by Suhama. We present a model for these complex developmental outcomes. These developmental patterns resemble those described previously and less completely for "secondary" OAs of cells with mirror-image global patterns, including janus cells. The present study demonstrates that such alterations in oral development are not a direct outcome of genotypic changes.

Effects of progesterone on the oviductal epithelium in estrogen-primed prepubertal beagles: light and electron microscopic observations

A total of 45 prepubertal beagles 6 to 8 weeks of age were used to study the cytological changes that accompany regression of the oviductal epithelium. The oviductal epithelium in untreated pups consisted of undifferentiated low cuboidal cells that measured 10.3 +/- 2.0 microns in height. In response to estradiol (E2), low cuboidal cells underwent hypertrophy, hyperplasia, and cytodifferentiation and gave rise to columnar ciliated and secretory cells. After 12 days of E2 treatment the epithelium was fully differentiated and measured 29.4 +/- 2.6 microns in height with 56% of the cells possessing cilia. When E2 treatment was continued for an additional 12 days, the epithelium was maintained in a differentiated state. However, if E2 treatment was terminated or progesterone (P) given alone or in conjunction with E2, the oviductal epithelium regressed and after 6 days was composed of low cuboidal cells that ranged in height from 9 to 14 microns with approximately 25% of the cells possessing cilia. A variety of cytological changes characterized the process of regression. The most immediate signs that regression was underway was a reduction in the height of the epithelium and the presence of cells with shrunken, pleomorphic nuclei that lacked prominent nucleoli. Degenerative events included: pinching off and shedding of the apical cytoplasm of cells comprising the epithelium, extrusion of whole cells and/or nuclei, and resorption of cilia and basal bodies. During the first 6 days following E2 withdrawal or P treatment, macrophages and cellular debris were frequently present within the lumen of the oviduct. The process of regression did not proceed synchronously throughout the ampulla of the oviduct, nor did all cells appear to degenerate in the same manner. The cytological changes that accompanied oviductal regression following P treatment were identical to those observed following E2 withdrawal. Results from experiments conducted in the present study show that: E2 induces the oviductal epithelium to differentiate and is required to maintain the epithelium in a differentiated state, E2 withdrawal or P treatment causes the oviductal epithelium to regress, at least three distinct degenerative processes are involved in the transition of columnar ciliated and secretory cells into low cuboidal cells, and regression does not occur synchronously throughout the ampulla region of the oviduct.